Rare earth magnets and magnet powders are used extensively in electromechanical devices such as motors and actuators. It is known that rare earth magnets and especially rare earth magnet powders are highly reactive toward oxygen, moisture and other chemical agents such as chloride ions. The use of such reactive rare earth magnet powders in bonded magnets limits their application frequently to temperatures under 100.degree. C. Inasmuch as rare earth magnets and rare earth magnet powders have been known for approximately 15 years, a need has existed with regard to their oxidative and corrosive stability, a need which has been heightened with the introduction of the iron-based rare earth magnet alloys.
An article "Effects of Surface Treatment for Thermoplastic Magnet" by Satoh, et al, IEEE Translation Journal on Magnetics in Japan, Volume TJMJ-1, No. 3, June 1985, page 387,388, disclosed the use of various coupling agents which are used to increase the loading of magnetic alloy powder and to improve the processing of the same material.
The article "Thermoplastic Magnet Having Highly Improved Heat-Resistance" by Satoh, et al, IEEE Translation Journal on Magnetics in Japan, Volume TJMJ-1, No. 8, November 1985, relates to the use of a heat resistant coupling agent which was utilized to coat SmCo.sub.5 powders.
Both of the above articles have graphs indicating dramatic drop off in magnetic properties at temperatures in excess of 100.degree. C. and essentially nonexistent magnetic properties at 200.degree. C.
European Patent Application 260,870 relates to corrosion resistant magnetic powders provided by treating magnetic particles with a solution containing chromate or dichromate ions and polymeric magnets containing the powder.
Japanese Patent Application 84/94433 filed May 14, 1984, relates to an anti-corrosive coating for metals containing ethylene vinylacetate polymers, acrylic polymers, or polyvinyl acetals; amino silanes; and epoxides. The compound forms a weather-resistant anti-corrosive coating for metals.
U.S. Pat. No. 4,241,116 to Taniyama et al relates to a method of treating the surface of a shaped polycarbonate resin. A first treating layer contains a bisphenol type epoxy resin. The article is then subsequently coated with a composition containing three different types of compounds, the first compound being the reaction mixture of an aminoalkylalkoxy silane with an epoxyalkylalkoxy silane, the second compound is a mixture of an alkyl-modified methylol melamine with an alkyl resin and the third compound is an acrylic acid derivative.
U.S. Pat. No. 4,558,077 to Gray relates to high glass transition temperature epoxy resins, that is polyglycidyl ethers of polyphenol alkanes, which are utilized to bond rare earth-iron alloy magnets.
U.S. Pat. No. 4,497,722 to Tsuchida relates to a plastic magnet composition utilizing a thermoplastic resin as a binder and a phosphorus containing compound having at least one phosphorus-to-oxygen linkage which is coated on the particle surface.
U.S Pat. No. 4,802,931 to Croat relates to magnetically hard compositions having high values of coercivity, remanence and energy product which contain rare earth elements, transition metal elements and boron in suitable proportions. The preferred rare earth-elements are neodymium and praseodymium, and the preferred transition metal element is iron. The magnetic alloys have characteristic very finely crystalline microstructures.